Cooling fins on spin on oil filters?

[Psmith]

I recently saw an extruded piece of Aluminum (cooling fins) that hose clamped arount an aircraft spin on filter. Anyone with experience with these? Are these STC'd.

Pete Smith 1320D 51 model A
Lewistown, MT

[cessna170bdriver]

I've seen these, and will admit to having no experience with them, so I don't know how well they work if at all. In any case, I'm not sure what the advantage would be on the C-145/O-300 installation in the 170. Maximum oil temperatures for these engines have been raised from the original 225 degrees F to 240 degrees F. The most I've ever seen on my '55 B model (different baffling from an A) in an extended climb (with no oil filter at all, only the original screens) is around 210 (gauge checked in boiling water before installation). My engine has 1700+ SMOH.

If you are having trouble keeping oil temperatures below 240 at all times (at least on land planes), you could have other problems, such as poor baffling or excessive blow-by that need to be dealt with directly.

Also if you are running in the 210 range normally and just want lower oil temp, remember that cooler is not always better. The higher temps do a better job of keeping the water and acids driven out of the oil.

All just my experience and MHO.

Miles

[Psmith]

Thanks Miles. My model A with ~ 400 SMOH and a C145 will have no problem seeing 225F on a 90F day during a cruise climb. Typically T/O is from a 7500'DA field with climb to a cruise DA of ~10,000. During cruise oil temp will reduce to something below 220. I am also running a 49 inch pitched prop. My oil temp typically runs 130F above ambient. I believe what I have is a normal 170?

Pete

[n3439d]

I have used them on my plane in the summer time. I have found it will drop the oil temp about 10 in cruise flight. In general I don't see a need for this small of a drop and only put it on for really hot days. On cool day the oil temp will not get high enough with it installed. I also have some mods that keep my cruise speed down around 95-100 thus cutting down the normal air flow over the oil pan.

ken

[Bruce Fenstermacher]

Miles and all. The 240 degree oil limit is only in effect when you are running straight 50W oil. If you are running anything else the limit is 225 degrees

[cessna170bdriver]

Thanks Miles. My model A with ~ 400 SMOH and a C145 will have no problem seeing 225F on a 90F day during a cruise climb. Typically T/O is from a 7500'DA field with climb to a cruise DA of ~10,000. During cruise oil temp will reduce to something below 220. I am also running a 49 inch pitched prop. My oil temp typically runs 130F above ambient. I believe what I have is a normal 170?

Pete

Pete, I run similar density altitudes for take-off and cruise, so your numbers sound fairly normal. Sounds like you should be OK as is, as long as you're running the straight 50wt. My prop is a 51-pitch so that might explain my slightly lower temps.

I had a friend many years ago who had an A-model he had to step climb due to high oil temps. He tried repairing baffling to no avail. I feel like his temps were real, as oil pressure began to drop as oil temp approached the redline.

Miles

PS: Thanks, Bruce for the info on the requirement for straight 50wt to use the higher oil temp redline. It's been discussed here before, and I've missed that point up 'til now.

[Psmith]

Miles, I run 20w50XC and on a 100 degree day, which is unusual out here, I too had to step climb but I did keep the OT at or below 225. The good thing about high OT is you are never concerned about not boiling the water off.
Pete

[zero.one.victor]

I bought a finned cooler-cover for the spin-on filter a few years ago. No "basis for approval", as George would say. Got it from JC Whitney, it's called a "Cool Collar" & goes for about $20. Didn't seem to make much difference, I think I ran it just that one summer. Probably a better mod to do instead of (or in addition to) the cool collar would be to run another blast tube to the oil filter, using scat hose.

Eric

[Dave Clark]

I bought a finned cooler-cover for the spin-on filter a few years ago. No "basis for approval", as George would say. Got it from JC Whitney, it's called a "Cool Collar" & goes for about $20. Didn't seem to make much difference, I think I ran it just that one summer. Probably a better mod to do instead of (or in addition to) the cool collar would be to run another blast tube to the oil filter, using scat hose.

Eric

Or do the "Arizona Mod" as I call it. Open the air entry below the prop to it's maximum to allow more air to go past the pan. I had a real problem with oil temps on the C145 until I did the mod. This really drops the temps a lot and can be plugged up with a winterization plate. It requires a new doubler inside and some riveting but less than an hours work. No approval basis but one would have to look real close and really know the airplane to notice it. The only problem with all of these "fixes" is maintaining a constant temperature without a vernatherm like on an oil cooler installation. So you have reasonable climb temps then the cruise temps are too low. But I'd rather have it that way. I think anything over 165 degrees will keep the moisture out. It would be nice to have a controllable slide valve for the AZ mod kind of like a cabin heat valve but....

Just another problem fixed by the 180 Lyc conversion. Oil temps stay locked on at about 170 degrees. Any weather, any climb or speed.

[zero.one.victor]

Miles, I run 20w50XC and on a 100 degree day, which is unusual out here, I too had to step climb but I did keep the OT at or below 225. The good thing about high OT is you are never concerned about not boiling the water off.
Pete

I run Phillips XC20-50 year around also, but I think if I lived where the temp's weren't so moderate ( what's a 100 degree day? ) I'd run the 20-50 in the winter & run straight-weight Aeroshell W100 when it got warm.

Eric

[GAHorn]

There's usually good reason to stick with "approved" modifications should you decide to alter your airplane. Unapproved mods not only diminish your aircraft's value (especially when the unapproved/undocumented mod is detected and the airplane becomes grounded due to it),... but they frequently are the brainchild of someone not experienced or educated in the area of expertise required to insure the mod is truly beneficial and/or the research for the alteration is inadequately documented or non-existant. The time and labor is a waste AND the aircraft is devalued.

The concept of cooling fins on an oil cooler is similar to that of a heat-sink on a transistor, or the fins in a radiator.... The intent is to shed heat from the base object (transistor or liquid coolant) to atmosphere. In order for that to transpire, the atmosphere must be cooler than the base object. Think about what transpires beneath the cowl of our airplanes.
Oil is heated by the engine to around 225 degrees F. (let's accept that as an illustration) The oil then is passed to an external spin-on filter. (That's the scenario we're discussing if we're discussing cooling fins on oil filters.) The spin on filter is sitting out in the cowling bathed in air-flow on it's way to exit the lower cowl....AFTER it's already passed over engine cylinders with head temperatures hovering around 350 degrees F, and EXHAUST pipes hovering around 1100-1350 degrees F. That air is quite warm. It is unlikely to absorb any more heat from an oil filter equipped with "cooling" fins. In fact, it's probably more accurate to call them "heating" fins because they are more likely to absorb the heat from the cowling air and pass it to the base unit, the oil filter.
(JC Whitney supplies auto parts, not aircraft parts. Autos run under-the-hood temps considerably cooler than aircraft, but even some autos can run under-hood temps around 500 degrees F. The difference is: JC Whitney is not exposed to safety-of-flight issues when their gimmick doesn't work as advertised.)

Engine cooling (and by association, oil cooling) in our aircraft depends upon a differential air pressure between the air above the cylinders and that below the cylinders. This facilitates the passage of the air through the cylinder cooling fins where it picks up heat, downward toward the cowling exit. Any increase in air pressure below the cylinders will inhibit this flow and diminish engine cylinder cooling. The oil system in our engines pumps oil thru the hollow pushrods up to the rocker-box area of the cylinders where the oil lubricates and cools (picks up heat from) the upper cylinder and valve train. The oil then drains back toward the oil sump/pan via the pushrod tube housings. Air-flow around the cylinders cools this oil as it flows back toward the sump.
(Meanwhile, nearby, the exhaust system risers are running 1100 degrees PLUS and if there is any leak from the riser-cylinder gasket and/or the riser-to-muffler clamp, it will blow hot exhaust onto the pushrod housings and will heat up the oil very quickly. A major cause of high oil temps in our engine installations is due to undetected/unrepaired exhaust leaks and/or engine baffling (including inter-cylinder baffling) either missing or in poor condition.)
Back to the high-pressure/low pressure air discussion: Anything that causes an increase in lower cowl air pressures will contribute to poor engine/oil cooling. Opening up the lower/forward oil sump blast-opening (the square hole below the prop-shaft flange) will increase lower cowl air pressures. More is not always better. In order for air to cool the sump, it must also flow at a speed sufficiently slow to allow it time to absorb the heat from the sump. Opening up that hole not only increases lower cowl air pressures (which detract from cylinder/oil cooling) but it also may have the exact opposite than the intended purpose by increasing the speed of that air passage. Air cooled engine cowls are a more complex animal than may first appear. INLET air is less likely to be needful of increase than EXIT air.
Aviation history is full of examples where operators have tried to reduce engine temps by increasing inlet air to no avail. But when the inlets were closed back to original and exits were opened up the engines cooled down nicely. (Look at the LoPresti mods on Mooney's and many Pipers. The cowl inlets are actually considerably smaller than predecessors, yet those higher performance engines which generate more heat actually run cooler with less drag than the original designs.) This is because the air pressure differential was increased by the larger exit. The Cessna 170 seaplane lip is another example of correct design and application of this principle.
Meanwhile, altering your aircraft in unapproved/undocumented ways does not favorably affect the airplane's value.

Also, be reminded that our oil temp gauges are cheap gauges. They fail frequently and they do not remain accurate forever. I have personal experience with two of them that failed, not like one would suspect...in the lower ranges..., but they failed by reading too high! A test with a known temp probe proved the gauge was reading 250 degrees when the oil was actually only 190! This has occurred twice on my own airplane. Replacement/repair of the gauge is the only thing to do in that case. Don't accept your gauge's accuracy as axiomatic.

[This msg is not intended to start a flame-war or find fault with owners who have every right to do what they wish to their own property. Hopefully it contains information our 170 friends may find useful.)

[Dave Clark]

OK fine George but we're talking OIL temps here and I'm just saying that the FACTORY designed an oil Pan cooling system to lower oil temperatures and that works well for most climates but can be modified slightly and it WILL get the oil temps down in the very hot climates.

Also mentioned was that it is not an approved mod so let everyone decide for themselves on whether to do it or not. I found it worked for me in AZ with no detriment in the moderate climate in Western WA.

[GAHorn]

OK fine George but we're talking OIL temps here and I'm just saying that the FACTORY designed an oil Pan cooling system to lower oil temperatures and that works well for most climates but can be modified slightly and it WILL get the oil temps down in the very hot climates.

I believe the factory had utilized the ability/money/engineering resources to know how big to make that opening and still be compatible with the differential air pressures they'd also designed into the cowling system. They did this with deliberate intent to keep the oil temperatures within limits, and still meet upper engine cooling requirements. Something has to malfunction before oil tempertures become excessive. If your airplane has excessive oil temps, then whatever malfunction which has occurred still exists if that is all you've done to change the indications. The original size opening for the oil sump is part of the certificated design.

Also mentioned was that it is not an approved mod so let everyone decide for themselves on whether to do it or not. I found it worked for me in AZ with no detriment in the moderate climate in Western WA.

The fact that your mod was unapproved is what prompted my opening statement "There's usually good reason to stick with "approved" modifications should you decide to alter your airplane." My closing statement included:"This msg is not intended to start a flame-war or find fault with owners who have every right to do what they wish to their own property." Even if it is illegal to operate the airplane like that.

If one wishes to remain legal, and if one believes one's actions were correct or a correction of a design deficiency, then one should apply for approval for the modification. (Keep in mind that an astute FAA inspector will observe that Cessna 170's were certificated to operate in AZ and will likely ask the question, "Did a malfunction occur to cause the high oil temps, and did this mod correct, or mask, that malfunction?")

[Dave Clark]

George I agree with your fine analysis of engine cooling design in the June 18th posting but I think you're missing my point here. You stated in your last post:

"I believe the factory had utilized the ability/money/engineering resources to know how big to make that opening and still be compatible with the differential air pressures they'd also designed into the cowling system. They did this with deliberate intent to keep the oil temperatures within limits, and still meet upper engine cooling requirements. Something has to malfunction before oil temperatures become excessive. If your airplane has excessive oil temps, then whatever malfunction which has occurred still exists if that is all you've done to change the indications. The original size opening for the oil sump is part of the certificated design."

About 30 years ago I was involved in the design and construction of a cowling and cooling system for a friend who was getting a multiple STC to put a 180 Lyc into the Aeronca Sedan. We worked very closely with the FAA and did extensive flight testing to determine the cooling was within the FAA guidelines. The flight test data was all corrected to standard day temperature at sea level. There was considerable latitude to change items like the lower cowl lip, baffles and such that would give different results for CHT and oil temps. So I think what the stock 170 setup is works well for most circumstances but with all other things being equal (good baffles, nothing wrong with the engine, etc.) The weak point is oil temperatures on a very hot day in a long climb.

So the factory engineered the airflow past the pan as an oil cooler substitute that works well on a standard day. They gave us the "winterization plate" to keep the oil warm on very cold days. They gave us nothing to cool the oil better on very hot days. The mod I'm talking about opens about 4 square inches into the lower cowl which does not seem to be significant or detrimental to cylinder head cooling and really does work well. I think it's better to do this minor change than to have to sit on the ground. I've done that, don't like it.

I've developed a half a dozen multiple STC's, numerous one time STC's and field approvals and have owned about 40 airplanes over my 30 year career as pilot and A&P IA. I know as the parts/maintenance coordinator you can't condone this mod and it's good for people to know the things you've mentioned for their consideration. As for resale value, I could have that mod fixed back to the stock size in about an hour.

[170C]

It has always been a curiosity to me why Continental did not design in oil coolers on its 100 horse + engines. We know they did on the 0-470 & larger ones. Lycoming has them on 0-235's & up. Maybe Cont'l. felt it just added complexity, cost & weight and that their engines were designed not to need them. However, as I am sure others have seen, in the Continental Aircraft Engine Illustrated Parts List for C-125, C-145 & O-300 Aircraft Engines Manual, on page 19 there is part # 530264 (oil cooler). I don't know if these were ever readily sold/installed, but apparently they were available at one time. I personally have never seen an O-300/C-145 with one, but its interesting that Cont'l. apparently felt there may have been a need for them in some installations.